Rotor system

ABSTRACT

A rotor system for a rotary wing aircraft such as a helicopter or the like wherein a main resilient bearing restrains movement of the blade against centrifugal forces imposed thereon while permitting movement of the blade about certain designated axes such as a lead-lag, a flapping and a pitch axis. A secondary resilient bearing cooperates with the main resilient bearing for restraining bodily movement of the blade transverse to its longitudinal axis and preventing the introduction of undesirable stresses into either of the resilient bearings without interfering with movement or substantially increasing the resistance to movement of the blade about the designated axes while insuring that such latter movements are generally about a point and/or axis generally coincident with the center of both resilient bearings.

United States Patent Gorndt 1 Oct. 24, 1972 [54] ROTOR SYSTEM PrimaryExaminer-Everette A. Powell, Jr.

[72] Inventor: John H. Gomdt, Erie, Pa. Attorney-James wnght [73]Assignee: Lord Corporation, Erie, Pa. [57] ABSTRACT [22] Filed: March 5,1971 A rotor system for a rotary wing aircraft such as a Appl. No.:121,425

Killian ..416/141 X helicopter or the like wherein a main resilientbearing restrains movement of the blade against centrifugal forcesimposed thereon while permitting movement of the blade about certaindesignated axes such as a leadlag, a flapping and a pitch axis. Asecondary resilient bearing cooperates with the main resilient bearingfor restraining bodily movement of the blade transverse to itslongitudinal axis and preventing the introduction of undesirablestresses into either of the resilient bearings without interfering withmovement or substantially increasing the resistance to movement of theblade about the designated axes while insuring that such lattermovements are generally about a point and/or axis generally coincidentwith the center of both resilient bearings.

11 Claims, 3 Drawing Figures PATENTEDHBT I912 3.700.352

,SHEET 1 or 2 VINVENTOR JOHN H. GORNDT BY WWW ATTORNEY PATENTEDHET24 m23.700352 SHEET 2 BF 2 Fig-3;

INVENTOR JOHN H. GORNDT WWMQW ATTORNEY ROTOR SYSTEM This inventionrelates to rotary wing aircraft such as helicopters or the like and moreparticularly to a rotor system and the means thereof for mounting theblade.

{ In conventional articulated rotor systems, it is customary to providefor each blade separate connections to the assignee of the presentinvention. As illustrated in the above referenced patent, theseresilient bearings include a body of elastomer and a plurality of spacedplates of a particular construction and arrangement embedded in andbonded to the body of elastomer. The resilient bearing is assembled inthe rotor system such that centrifugal forces imposed on the blade areresiliently restrained while designed for articulated movements of theblade relative to the rotor hub are permitted. For instance in a fullyarticulated rotor system where movements of each blade about a leadlag,a flapping and a pitch ,axis are to be accommodated, the resilientbearing may comprise a body of elastomer disposed in load carryingrelation between the blade and rotor hub such that centrifugal forcesimposed on the blade load the body of elastomer in compression whilemovements of the blade about the lead lag, flapping and pitch axes loadthe body of elastomer primarily in shear. In order to increase thecompressive load carrying ability of the body of elastomer in adirection along the longitudinal axis of the blade without interferingwith movement of the blade about the above mentioned axes, a pluralityof spaced segmented spherical shaped plates of relatively nonextensiblematerial are disposed transversely of the longitudinal axis of the bladeand embedded in and bonded to the body.

However, in a resilient bearing such as that briefly described above,the same is subject to deformation or deflection in directions generallytransverse to the longitudinal axis of the blade. As a result bladeshear loads or forces on the blade transverse thereto cause undesirablebodily movements of the blade which result in imbalance of the rotorsystem to induce undesirable vibrations. In addition to the vibrationproblems discussed above, such blade shear loads induce additional andunnecessary stresses into the resilient bearing which substantiallyreduce the fatigue life thereof. Thus, it is highly desirable tointroduce means into such a rotor system for carrying blade shear loads.

Suggested solutions to this problem, in fully articulated systems, areillustrated in Gomdt et al., U. S. Pat. No. 3,111,172, issued Nov. 19,1963 and assigned to the assigriee of the present invention and inMosinskis, U. S. Pat. No. 3,501,250, issued Mar. 17, 1970. In theMosinskis patent there is disclosed in cooperation with a main resilientbearing such as that briefly described above, a universal bearingincluding a socket fixed to the rotor hub and a ball rotatably mountedin the socket. The blade includesa supporting shaft rotatable ble forreasons that need not be discussed.

The last mentioned Gomdt et .al. patent, U. S. Pat. No. 3,111,172,discloses a resilient universal bearing which cooperates with a mainresilient bearing as described above for carrying blade shear loads. Theutilization of such a resilient universal bearing does not include anyfrictionally engaging surfaces. While such a resilient universal bearingis believed to be advantageous over the arrangement illustrated in theMosinskis patent, it too has its problems. First, the resilientuniversal bearing is constructed and arranged relative to the mainresilient bearing to be neutral or undeflectedwhen the rotor system isinoperative. As a result, during operation of the: rotor system, theresilient universal bearing is deflected or stressed which stresses aredetrimental to the fatigue life of such a bearing. Second, the center ofthe resilient universal bearing is generally coincident with thespherical center of the main bearing when the rotor system isinoperative. Thus, during operation of the rotor system, the respectivecenters of the resilient bearings are spaced from one'another.Accordingly, lead-lag and flapping movements of the blade establishunnecessary stresses in both the resilient bearings which aredetrimental to the fatigue life thereof. In addition, the resistance ofthe bearings to movements of the blade about lead-lag, flapping andpitch axes is unnecessarily high.

It is an object of the present invention to provide in a rotor systemhaving a main resilient bearing for restraining the blade againstcentrifugal forces while permitting movement of the blade about certaindesignated axis, an improved resilient bearing for cooperating with themain resilient bearing to restrain bodily movement of the bladetransverse to its longitudinal axis without interfering with movement ofthe blade about the designated axis.

Another object of the present invention is to provide in such a rotorsystem a resilient hearing which operates in a neutral or undeflectedposition during normal operation of the rotor system to restrain bodilymovement of the blade transverse to its longitudinal axis.

A further object of the present invention is to provide in such a rotorsystem a resilient bearing which cooperates with the main resilientbearing to insure that movements of the blade about certain designatedaxis are generally about a point and/or axis generally coincident withthe center of both resilient bearings to prevent the establishment ofunnecessary stresses in each of the bearings.

Briefly, the objects of the present invention are accomplished in arotor system including a rotor hub rotatable about a central axis, atleast one sustaining blade, and means connecting the blade to the rotorhub with the blade normally extending generally radially from the hubfor rotation therewith about the central axis. The connecting meanscomprises a member fixed to the blade having a surface extendingtransverse to the longitudinal axis of the blade and spaced from andpresented toward the blade and away from the rotor hub and a memberfixed to the rotor hub having a surface extending transverse to thelongitudinal axis of the blade and spaced radially outward and presentedtoward the first surface. In a preferred arrangement the members areyokes carried by the rotor hub and blade, respectively, which are linkedthrough each other and lie, respectively, in intersecting planes. A mainresilient bearing is disposed between the surfaces and has its axis ofgreatest stiffness along the longitudinal axis of the blade and axes ofless stiffness perpendicular or transverse to the longitudinal axis ofthe blade for resiliently restraining the blade against centrifugalforces imposed thereon in response to rotation of the rotor hub whilepermitting movement of the blade about the axes of less stiffness. In afully articulated rotor system, the main resilient bearing typicallytakes the form 'of a body of elastomer disposed between and fixedlysecured to the spaced surfaces and a plurality of spaced segmentedspherical shaped plates of relatively nonextensible material disposedtransversely of the iongitudinal axis of the blade and embedded in andbonded to the body with their spherical centers coinciding with thelongitudinal axis of the blade such that the body of elastomer andplurality of plates cooperate to restrain movement of the blade againstcentrifugal forces imposed thereon while permitting pivotal movement ofthe blade about lead-lag and flapping axis and rotation about a pitchaxis.

A secondary resilient bearing is connected between the blade and rotorhub which has its axes of greatest stiffness perpendicular or transverseto the longitudinal axis of the blade and an axis of less stiffnesscoincident with the axis of greatest stiffness of the main resilientbearing means. The secondary resilient bearing is normally positioned ina predeflected position along the longitudinal axis of the blade duringnonrotation of the rotor hub and is movable along the longitudinal axisof the blade to a neutral or undeflected position in response tomovement of the blade as a result of centrifugal forces imposed thereon.With the secondary resilient bearing having its axes of greateststiffness perpendicular or transverse to the longitudinal axis of theblade, it will be apparent that the same cooperates with the mainresilient bearing to restrain movements of the blade transverse to thelongitudinal axis of the blade. By having the secondary resilientbearing movable to a neutral position during normal operation of therotor system, no unnecessary stresses remain in the secondary resilientbearing and, thus, the fatigue life of such bearing is optimized.Furthermore, by having the secondary resilient bearing predeflected andmovable to a neutral position, provisions can be made to insure that thecenter of the secondary resilient bearing coincides with axes ofdesignated movements of the blade and the center of the main resilientbearing such that during the movements of the blade about suchdesignated axes only the necessary stresses are introduced into theresilient bearings to further optimize the fatigue life thereof andminimize the resistance to movement of the blade about these axes. Thestiffness of the secondary resilient bearing along axes perpendicular ortransverse to the longitudinal axis of the blade may be and ispreferably increased by the provision of at least one annular plate ofrelatively nonextensible material disposed in the elastomerconcentricall about the longitudinal axis of the blade.

Some of the objects of the invention having been stated, other objectswill appear as the description proceeds, when taken in connection withthe accompanying drawings, in which:

FIG. 1 is a fragmentary top plan view with portions in sectionillustrating a rotor system of the present invention; 7

FIG. 2 is a fragmentary side elevational view with parts in section ofthe rotor system of FIG. 1; and

FIG. 3 is an enlarged view similar to FIG. 2 with the upper portionthereof illustrating the rotor system in a nonoperating position and thelower portion illustrating the rotor system in an operating position.

Referring more specifically to the drawings wherein like referencecharacters are employed to indicate like parts, there is shown in FIGS.1 and 2 a rotor system, generally indicated at 10, illustrating thepreferred embodiment of the present invention. While the rotor system10, to be hereinafter described, is for a fully articulated system, theconcepts of the present invention apply to less than fully articulatedsystems and to systems having any number of blades. Since theconnections typically are the same for each blade, only that associatedwith a single blade will be described.

As illustrated, the rotor system 10 comprises a drive shaft 11 which isrotatable driven by drive means, not shown, about its longitudinal orcentral axis 12. A rotor hub 13 is concentrically mounted on the driveshaft 1 l for driving rotation thereby about the central axis 12. Asustaining blade 15 is connected to the rotor hub 13 by means, generallyindicated at 20, with the blade 15 normally extending generally radiallyfrom the rotor hub 13 for rotation therewith.

As is well known in a fully articulated rotor system 10, the means 20connecting the blade 15 to the rotor hub 13 must restrain movement ofthe blade 15 against centrifugal forces imposed thereon while providingfor pivotal movement of the blade 15 relative to the rotor hub 13 abouta lead-lag or sometimes referred to as drag axis, a flapping axis andfor rotation about a pitch or feathering axis. The lead-lag axis is in avertical plane through the rotor hub 13 and, thus, is for movement ofthe blade 15 relative to the rotor hub 13 in the plane of rotation ofthe blade 15. The flapping axis is in a horizontal plane through therotor hub 13 and is for movement of the blade 15 relative to the rotorhub 13 in a plane perpendicular to the plane of rotation of the rotorhub 13. These lead-lag and flapping motions are typically associatedwith aerodynamic affects on the blade 15, the weight of the blade 15 andchanges in speeds of rotation of the blade 15 about the central axis 12.The pitch axis is coincident with the longitudinal axis of the blade 15and, thus, is for rotation of the blade 15 about its own longitudinalaxis. Pitch motions are movements involved in maneuvering the aircraftand are required in all conventional vertical take-off and landingaircraft such as helicopters and the like. Pitch control means, notshown, are provided for imparting the desired pitch motion to the blade15.

The means 20 connecting the blade 15 to the rotor hub 13 includes a yoke21 disposed in the plane of rotation of the rotor hub 13 and carried bythe rotor hub 13. The radially outward end of yoke 21 has a hub 22having a closed end and an open and carried thereby disposedconcentrically about the longitudinal axis of the blade with the openend thereof extending radially from the rotor hub 13. On the closed endof the hub 22 there is mounted an outer plate member 23 that defines asurface 24 extending transverse to the longitudinal axis of the blade 15and facing radially inward toward the rotor hub 13. The surface 24preferably has a spherical curvature with the spherical center thereofcoinciding with the longitudinal axis of the blade 15 radially outwardof the surface 24 from the rotor hub 13.

A yoke 25 is disposed radially outward of yoke 21 and lies in a planewhich intersects the plane of yoke 21. The yokes 21 and 25 are linkedthrough each other. The blade 15 is suitably connected to the radiallyoutermost portion of yoke 25 to extend radially from the rotor hub 13.The radially innermost end of yoke 25 has an inner plate member 26mounted thereto which defines a surface 28 extending transverse to thelongitudinal axis of the blade 15 and spaced radially inward of surface24. The surface 28, preferably, has-a spherical curvature with thespherical center thereof coinciding with the longitudinal axis of theblade 15 radially outward of the surface 28. Thus, surfaces 24 and 28are disposed in opposed and presented toward each other relation. v

A main resilient bearing, generally indicated at 30, connects yokes 21and 25 and comprises a body 31 of elastomeric material such as naturalor synthetic rubber which is disposed between and has opposite endsthereof fixedly secured such as by bonding to the surfaces 24 and 28. Inthe construction here illustrated, opposite ends of the body 31 ofelastomer conform and are bonded to the surfaces 24 and 28 of plates 23and 26, respectively. The plates 23 and 26 are preferably detachablycarried by yokes 21 and 25, respectively. Thus, the body 31 of elastomermay be bonded to the plates 23 and 26 prior to their assemblywith themain body of yokes 21 and 25. v

With the body 31 of elastomer so disposed, centrifugal forces imposed onthe blade in response to rotation thereof will be resiliently restrainedby compression loading of the body 31 of elastomer. Since thecentrifugal forces imposed on the blade are quite large, it is desirableto include a plurality of shims or plates 32 of metal or other suitablenonextensible material spaced throughout the body 31 of elastomer whichextend transversely of the longitudinal axis of the blade and areembedded in and bonded to the body 31. In the arrangement hereillustrated, the plurality of plates 32 are spaced segmented sphericalshaped plates disposed transverse to the longitudinal axis of the blade15 with their spherical centers coinciding with the longitudinal axis ofthe blade radially outward from the rotor hub 13 and outwardly of bothsurfaces 24 and 28. While the spaces between the plates 32 are indicatedas being nonuniform, such nonuniformity does not form a part of thepresent invention. The plates 32 divide the body 31 of elastomer toprevent bulging thereof under compression loading to thereby increaseits stiffness along an axis coincident with the longitudinal axis of theblade 15. On the other hand, the plates 32 do not materially affect thestiffness of the body 31 in shear and, accordingly, do not affect theresistance of the main resilient bearing 30 in accommodating lead-lag,flapping and pitch movements of the blade 15. Thus, the body 31 ofelastomer and plurality of plates 32 cooperate to resiliently restrainthe blade 15 against centrifugal forces imposed thereon in response torotation of the rotor hub 13 without significant deflection thereofwhile permitting movement of the blade 15 about the lead-lag, flappingand pitch axes.

In the preferred arrangement of the present invention, it is desirablethat the spherical centers of the surfaces 24 and 28 and of each of thespherical plates 32 coincide at a common point 40 during normaloperation of the rotor system 10. While this may be difiicult to obtainin practical application, for general purposes of the present inventionit can be assumed that during non-operation and operation of the rotorsystem, the spherical centers of the surfaces 24 and 28 and segmentedspherical plates 32 generally coincide about a common or fixed point 40which is coincident with the longitudinal axis of the blade 15. Byhaving such a coincident center during normal operation of the rotorsystem, the lead-lag, flapping and pitch axes will intersect at thecoincident center 40 and all movements of the blade 15 will take placeabout this coincident center 40. I

In a rotor system where the main resilient bearing 30 as described aboveis the only means connecting the blade 15 to the rotor hub.13, it willbe apparent that blade shear loads or loads on the blade 15 transverseto its longitudinal axis will tend to deflect the main resilient bearing30 and thus, allow bodily movement of the blade 15. Such bodilymovements of the blade establish an imbalance in the entire rotor system10 which imbalance induces undesirable vibrations into the rotor system.Furthermore, such bodily movements introduce unnecessary stresses intothe body 31 of elastomer and, thus, contribute to a reduction in thefatigue life thereof. In addition, there is no positive assurance thatlead-lag, flapping and pitch movements of the blade 15 take place aboutthe common or fixed point 40.

In accordance with the present invention there is provided a secondaryor universal resilient bearing, generally indicated at 50, which isconnected between the blade 15 and rotor hub 13 and cooperates with themain resilient bearing 30 to restrain bodily movement of the blade 15transverse to the longitudinal axis thereof, and to positively insurethat lead-lag, flapping and pitch movements of the blade 15 take placeabout the common or fixed point 40 without interfering with lead-lag,flapping and pitch movements of the blade 15.

The resilient universal bearing 50 comprises an elongate member 51disposed between the blade 15 and rotor hub 13 radially outward of themain resilient bearing 30 with its longitudinal axis being coincidentwith the longitudinal axis of the blade 15. The outermost end ofelongate member 51 is detachably connected to yoke 25 which, ashereinbefore described, is in turn connected to the blade 15 and ismovable therewith. The innermost end of the member 51 is sphericalshaped in the form of a ball 52 with its spherical center 53 beingcoincident with the longitudinal axis of the blade 15. In thenonoperating condition of the rotor system 10 as illustrated in FIGS. 1and 2, the spherical center 53 of ball 52 is disposed radially inward ofcommon or fixed center 40 of the main resilient bearing 30 a distancepreferably equivalent to the radial displacement of the blade 15 duringnormal operation of the rotor system 10. As illustrated the hub 22 ofyoke 21, carried by the rotor hub 13, is concentrically disposed aboutthe' elongate member 51. An annular socket 54 is carried inwardly of hub22 concentrically about the longitudinal axis of the blade 15 indiametrically opposed relation to the common or fixed center 40 of themain resilient bearing 30. Preferably, as illustrated, the socket 54 isdetachably connected to the hub 22 by suitable means such as a retainingring 55 and defines a longitudinally extending concave surfaceconcentrically about the longitudinal axis of the blade 15.

'An annular body 56 of elastomer is concentrically disposed about thelongitudinal axis of the blade 15 between the ball 52 and socket 54 andbonded thereto respectively, for resiliently interconnecting the same.In construction and assembly of the resilient universal bearing 50, thebody 56 of elastomer is connected between the ball 52 and socket 54 suchthat during normal operation of the rotor system 10, the body 56 ofelastomer is in a neutral or undeflected condition, that is, when thespherical center 53 of the ball 52 is coincident with the common orfixed center 40 of the main resilient bearing 30. Thus, duringnonoperation of the rotor system 10, FIGS. 1 and 2, the body 56 ofelastomer is predeflected.

With reference to FIG. 3, there is shown in the upper half therelationship of the resilient bearings 30 and 50 during nonoperation ofthe rotor system and in the lower half their relationship during normaloperation of the rotor system 10. During normal operation centrifugalforces imposed on the blade resiliently compress main resilient bearing30 a limited amount and move the ball 52 such that its spherical center53 coincides with the common or fixed center 40 of the main resilientbearing 30 and move the body 56 of elastomer to a neutral or undefiectedposition.

From the foregoing description, it will be apparent that blade shearloads or loads on the blade 15 transverse to the longitudinal axisthereof are resisted by compression loading of the resilient universalbearing 50. The load carrying ability or stiffness of the resilientuniversal bearing 50 may be and preferably is increased by the inclusionof at least one and preferably a plurality of spaced annular segmentedspherical shaped plates 58 of metal or other relatively nonextensiblematerial disposed between the ball 52 and socket 54 and embedded in andbonded to the annular body 56 of elastomer. As illustrated in the lowerhalf of FIG. 3, the plates 58 are concentrically disposed relative toeach other with their spherical centers coinciding with the sphericalcenter of ball 52 and the common or fixed center 40 of the mainresilient bearing during normal operation of the rotor system 10. Whilethe resilient universal bearing 50 cooperates with the main resilientbearing 30 to carry blade shear loads or loads transverse to thelongitudinal axis of the blade 15, numerous other advantages areprovided. First, both the main and universal resilient bearings 30 and50 are forced to operate about a coincident center. Such operationprevents the establishment of the imbalance problems previouslydiscussed and insures that lead-lag, flapping and pitch movements of theblade 15 only introduce necessary forces into the bearings 30 and 50 toprolong the fatigue lives thereof. Second, the resilient universalbearing 50 operates from a neutral position to prolong the fatigue lifethereof. Third, the cooperation of bearings 30 and 50 to operate about acoincident center minimizes the resistance to movements of the blade 15about its lead-lag, flapping and pitch axes while providing the otherenumerated advantages.

In the drawings and specification, there has been set forth a preferredembodiment of the invention and,

although specific terms are employed, they are used in a generic anddescriptive sense only and not for purposes of limitation.

What is claimed is: l. A rotor system for a rotary wing aircraft such asa helicopter or the like comprising a rotor hub rotatable about acentral axis, at least one sustaining blade, and means connecting saidblade to said rotor hub with said blade normally extending generallyradially from said hub for rotation therewith about said central axis,said connecting means comprising a member fixed to the blade having afirst surface extending transverse to the longitudinal axis of saidblade and spaced from and presented toward said blade and away from saidrotor hub, a member fixed to the rotor hub having a second surfaceextending transverse to the longitudinal axis of said blade and spacedradially outward of and presented toward said first surface, mainresilient bearing means disposed between said surfaces and having itsaxis of greatest stiffness along the longitudinal axis of said blade andaxes of less stiffness transverse to the longitudinal axis of saidblade, said main bearing means resiliently restraining said bladeagainst centrifugal forces imposed thereon in response to rotation ofsaid rotor hub,

a resilient secondary bearing means connected between said blade androtor hub and having its axes of greatest stiffness transverse to thelongitudinal axis of said blade and an axis of less stiffness coincidentwith the axis of greatest stiffness of said main resilient bearing meansand the longitudinal axis of said blade, said secondary bearing meansbeing normally positioned in a predeflected position along thelongitudinal axis of said blade during nonrotation of said rotor hub andbeing movable along the longitudinal axis of said blade to asubstantially neutral position in response to resilient movement of saidblade relative to said rotor hub as a result of centrifugal forcesimposed thereon during rotation of said rotor hub, said secondarybearing means cooperating with said main bearing means to carry forcestransverse to the longitudinal axis of said blade.

2. A rotor system as set forth in claim 1, wherein said main resilientbearing means comprises a body of elastomer disposed between and fixedlysecured to said surfaces, and

a plurality of spaced plates of relatively nonextensible materialdisposed transversely of the longitudinal axis of said blade andembedded in and bonded to said body of elastomer,

3 7 O 3 5 2 W2." 1 said body of elastomer and plates cooperating duringpredefiected position along the longitudinal axis rotation of said rotorhub to resiliently restrain said blade against centrifugal forcesimposed thereon along the longitudinal axis of said blade by loadingsaid body substantially solely in compression.

of said blade during non-rotation of said rotor hub and being movablealong the longitudinalaxis of said blade to a substantially neutralposi- 3. A rotor system as set forth inclaim 1, wherein said resilientsecondary bearing means comprises an elongate member disposed betweensaid blade and rotor hub having its longitudinal axis coinsubstantiallycoincident with said common cident with the longitudinal axis of saidblade, one i so h t d i r al nati n f aid end of said member beingfixedly connected to one rotor h b, 1 d-1 fl i d i h dj of said bladeand rotor hub and the other of Said ment and/or movements of :said bladerelative to blade and rotor hub having means concentrically said rotor hb ill b about id common point disposed about Said elongate member inspaced and forces on said blade transverse to the lonrelation thereto,

an annular body of elastomer disposed about the longitudinal axis ofsaid blade and being fixedly gitudinal axis thereof will be resisted bysaid universal bearing along its axes of greatest stiffness.

secured between the other end of said elongate member and said meansconcentrically of said elongate member, and

at least one annular elongate plate of relatively nonextensible materialconcentrically disposed about said elongate member and embedded in andbonded to said body of elastomer for increasing the load carryingability or stiffness of said body along axes transverse to thelongitudinal axis of 5. A rotor system, as set forth in claim 4, wherein20 said resilient universal bearing means comprises an elongate memberdisposed between said blade and rotor hub and having its longitudinalaxis coincident with the longitudinal axis of said blade, one end ofsaid member being fixedly connected to one of said blade and rotor huband the other end of said member being spherical shaped, the other ofsaid blade and rotor hub having means concentrisaid blade. 4. A rotorsystem for a rotary wing aircraft such as a g g g zfif ggg g f SphencalShaped porno helicopter or the like comprising g an annular body ofelastomer concentrically disposed about the longitudinal axis of saidblade between said spherical shaped portion of said elona rotor hubrotatable about a central axis, at least one sustaining blade, and meansconnecting said blade to said rotor hub with said blade normallyextending generally radially gate member and said means concentricallydisposed about said spherical shaped portion,

from said hub for rotation therewith about said central axis, saidconnecting means comprising at least one afmular segmenied sphenfialShaped a member fixed to the blade having a first Surface plate ofrelatively nonextensrble material concenextending transverse to thelongitudinal axis of tflcally dlsPosed about Said sphencal Shaped P saidblade and Spaced from and presented tron of said elongate member andembedded in toward said blade and away from said rotor hub, f boflded toSaid n f of elastfmer for a member fixed to the rotor hub having asecond mfireasmg the load carrymg ablhty i of surface extendingtransverse to the longitudinal salfi body Plong axes transverse to 'faxis of said blade and spaced radially outward of ms Sald blade wlthoutsubstafltlally i and presented toward Said fi t surface the resistanceto movement of said blade relative a first body of elastomer disposedbetween and fixto said rotor hub about 531d lead'lag, pp and edlysecured to said surfaces,

pitch axes.

6. A rotor system for a rotary wing aircraft such as a helicopter or thelike comprising a rotor hub rotatable about a central axis,

at least one sustaining blade, and

means connecting said blade to said rotor hub with a plurality of spacedsegmented spherical shaped plates of relatively nonextensible materialdisposed transversely of the longitudinal axis of said blade andembedded in and bonded to said body with their spherical centerscoinciding with the longitudinal axis of said blade, said first body ofelastomer and plurality of plates cooperating to carry substantiallysolely in comsaid blade normally extending generally radially from saidhub for rotation therewith about said central axis, said connectingmeans comprising pression centrifugal forces imposed on said a memberfixed to the blade having a first surface blade in response to rotationof said rotor hub extending transverse to the longitudinal axis of whilepermitting pivotal movement of said blade Said blade and spaced from andpresented about lead-lag and flapping axis and rotation toward Saidblade and away from said rotor hub, about a pitch axis, said lead-lagand flapping axis a member fixed to the rotor hub having a second i t rti at a rally n point al ng surface extending transverse to thelongitudinal said pitch axis, axis of said blade and spaced radiallyoutward of a resilient universal bearing means connected and presentedtoward said first surface,

between said blade and rotor hub and having its resilient main bearingmeans disposed between axes of greatest stiffness transverse to thelonsaid surfaces resiliently restraining said blade gitudinal axis ofsaid blade and axes of less stiffness about its center, said universalbearing means being normally positioned in a against centrifugal forcesimposed thereon in response to rotation of said rotor hub whilepermitting pivotal movement of said blade about lead-lag and a flappingaxis and rotation about a pitch axis with said lead-lag and flappingaxes intersecting at a substantially common point along said pitch axis,

between said 'blade and rotor hub having a center coincident with saidpitch axis, said universal bearing means being normally positioned in apredetlected position along the longitudinal axis of said blade duringnonrotation of said rotor hub and being movable along the longitudinalaxis of said blade toward a neutral position in response to resilientmovement of said blade relative to said rotor hub as a result ofcentrifugal forces imposed on said blade during rotation of said rotorhub to a point where its center is substantially coincident with theintersection of said leadlag and flapping axes with said pitch axis sothat during normal rotation of said rotor hub lead-lag, flapping andpitch adjustments and/or movements of said blade relative to said rotorhub will be about a common point. 7. A rotor system, as set forth inclaim' 6, wherein said resilient universal bearing means comprises asocket carried by one of said blade and rotor hub, a ball spacedinwardly of said socket and carried by the other of said blade and rotorhub, and elastomeric means resiliently interconnecting said ball andsocket. 8. A rotor system for a rotary wing aircraft such as ahelicopter or the like comprising a rotor hub rotatable about a centralaxis, at least one sustaining blade, and means connecting said blade tosaid rotor hub with said blade normally extending generally radiallyfrom said hub for rotation therewith about said central axis, saidconnecting means comprising a member fixed to the blade having a firstsurface extending transverse to the longitudinal axis of said blade andspaced from and presented toward said blade and away from said rotorhub,

a member fixed to the rotor hub having a second surface extendingtransverse to the longitudinal axis of said blade and spaced radiallyoutward of and presented toward said first surface,

a first body of elastomer disposed between and fixedly secured to saidsurfaces,

a plurality of spaced generally concentric segmented spherical shapedplates of relatively nonextensible material disposed transversely of thelongitudinal axis of said blade and embedded in and bonded to said bodyof elastomer with their spherical centers coinciding at a: generallyfixed center coincident with the longitudinal axis of said blade,

said first body of elastomer and spherical plates cooperating toresiliently restrain said blade against centrifugal forces imposedthereon in response to rotation of said rotor hub along the longitudinalaxis of said blade while permitting pivotal movement of said blade aboutlead-lag and flapping axes and rotation about a pitch axis, which axesintersect at said generally fixed center,

resilient universal bearing means connected a socket carried by one ofsaid blade and rotor hub,

a ball spaced inwardly of said socket and carried by the other of saidblade and rotor hub with its center located along said pitch axis andelastomeric means resiliently interconnecting said ball and socket,

said ball and socket being normally resiliently displaced relative toeach other axially of the longitudinal axis of said blade duringnonrotation of said rotor hub and being movable along the iongitudinalaxis of said blade to a substantially neutral position where the centerof said ball is generally coincident with said fixed center in responseto centrifugal forces imposed on said blade whereby said bearingscooperate to resist movement of said blade transverse to theiongitudinal axis of said blade while permitting pivotal and rotationalmovement of said blade about said coincident centers.

9. A rotor system, as set forth in claim 8 wherein said elastomericmeans comprises a second body of elastomer and at least one annularspherical shaped plate of relatively nonextensible materialconcentrically disposed between said ball and socket and embedded in andbonded to said second body of elastomer, said plate having its sphericalcenter generally coincident with said coincident centers when said balland socket are in said neutral position for increasing the load carryingability or stiffness of said second body of elastomer along axestransverse to the longitudinal axis of said blade without substantiallyaffecting the resistance to movement of said blade relative to saidrotor hub about said lead-lag, flapping and pitch axes.

10. A rotor system for a rotary wing aircraft such as a helicopter orthe like comprising a rotor hub rotatable about a central axis,

. first yoke means carried by said rotor hub and extending radiallyoutward therefrom,

second yoke means disposed radially outward of said first yoke means,sustaining blade connected to said second yoke means and extendingradially outward from said rotor hub, said yoke means being linkedthrough each other and lying respectively in intersecting planes, saidfirst yoke means having a first surface extending transverse to thelongitudinal axis of said blade facing radially inward toward said rotorhub, said second yoke means having a surface extending transverse to thelongitudinal axis of said blade spaced radially inward of said firstsurface and presented toward said first surface in opposed relationthereto,

a body of elastomer disposed between and fixedly secured to said firstand second surfaces,

plurality of spaced segmented spherical shaped plates of relativelynonextensible material concentrically disposed transversely of thelongitudinal axis of said blade and embedded in and bonded to said bodyof elastomer with their spherical centers coinciding with thelongitudinal axis of said blade radially from said rotor hub outwardlyof said first and second surfaces, said body of elastomer and pluralityof plates cooperating to resiliently restrain said blade againstcentrifugal forces imposed thereon in response to rotation of said rotorhub while permitting pivotal movement of said blade about lead-lag andflapping axes and rotation about a pitch axis, said axes intersecting ata generally fixed center along said pitch axis, and

a resilient universal bearing connected between said first and secondyoke means radially outward of said body of elastomer having a centerlocated along said pitch axis resiliently restraining movement of saidblade transverse to said pitch axis while permitting pivotal movement ofsaid blade about said lead-lag and flapping axes and rotation about saidpitch axis, the center of said universal bearing being positioned inpredeflected position along said pitch axis from said fixed centerduring nonrotation of said rotor hub and being movable along said pitchaxis to a substantially neutral position where its center is generallycoincident with said fixed center in response to centrifugal forcesimposed on said blade.

11. A rotor system as set forth :in claim 10, wherein the center of saidresilient universal bearing is positioned in a predeflected positionspaced along said pitch axis from said fixed center radially inwardtoward said rotor hub.

1. A rotor system for a rotary wing aircraft such as a helicopter or thelike comprising a rotor hub rotatable about a central axis, at least onesustaining blade, and means connecting said blade to said rotor hub withsaid blade normally extending generally radially from said hub forrotation therewith about said central axis, said connecting meanscomprising a member fixed to the blade having a first surface extendingtransverse to the longitudinal axis of said blade and spaced from andpresented toward said blade and away from said rotor hub, a member fixedto the rotor hub having a second surface extending transverse to thelongitudinal axis of said blade and spaced radially outward of andpresented toward said first surface, main resilient bearing meansdisposed between said surfaces and having its axis of greatest stiffnessalong the longitudinal axis of said blade and axes of less stiffnesstransverse to the longitudinal axis of said blade, said main bearingmeans resiliently restraining said blade against centrifugal forcesimposed thereon in response to rotation of said rotor hub, a resilientsecondary bearing means connected between said blade and rotor hub andhaving its axes of greatest stiffness transverse to the longitudinalaxis of said blade and an axis of less stiffness coincident with theaxis of greatest stiffness of said main resilient bearing means and thelongitudinal axis of said blade, said secondary bearing means beingnormally positioned in a predeflected position along the longitudinalaxis of said blade during nonrotation of said rotor hub and beingmovable along the longitudinal axis of said blade to a substantiallyneutral position in response to resilient movement of said bladerelative to said rotor hub as a result of centrifugal forces imposedthereon during rotation of said rotor hub, said secondary bearing meanscooperating with said main bearing means to carry forces transverse tothe longitUdinal axis of said blade.
 2. A rotor system as set forth inclaim 1, wherein said main resilient bearing means comprises a body ofelastomer disposed between and fixedly secured to said surfaces, and aplurality of spaced plates of relatively nonextensible material disposedtransversely of the longitudinal axis of said blade and embedded in andbonded to said body of elastomer, said body of elastomer and platescooperating during rotation of said rotor hub to resiliently restrainsaid blade against centrifugal forces imposed thereon along thelongitudinal axis of said blade by loading said body substantiallysolely in compression.
 3. A rotor system as set forth in claim 1,wherein said resilient secondary bearing means comprises an elongatemember disposed between said blade and rotor hub having its longitudinalaxis coincident with the longitudinal axis of said blade, one end ofsaid member being fixedly connected to one of said blade and rotor huband the other of said blade and rotor hub having means concentricallydisposed about said elongate member in spaced relation thereto, anannular body of elastomer disposed about the longitudinal axis of saidblade and being fixedly secured between the other end of said elongatemember and said means concentrically of said elongate member, and atleast one annular elongate plate of relatively nonextensible materialconcentrically disposed about said elongate member and embedded in andbonded to said body of elastomer for increasing the load carryingability or stiffness of said body along axes transverse to thelongitudinal axis of said blade.
 4. A rotor system for a rotary wingaircraft such as a helicopter or the like comprising a rotor hubrotatable about a central axis, at least one sustaining blade, and meansconnecting said blade to said rotor hub with said blade normallyextending generally radially from said hub for rotation therewith aboutsaid central axis, said connecting means comprising a member fixed tothe blade having a first surface extending transverse to thelongitudinal axis of said blade and spaced from and presented towardsaid blade and away from said rotor hub, a member fixed to the rotor hubhaving a second surface extending transverse to the longitudinal axis ofsaid blade and spaced radially outward of and presented toward saidfirst surface, a first body of elastomer disposed between and fixedlysecured to said surfaces, a plurality of spaced segmented sphericalshaped plates of relatively nonextensible material disposed transverselyof the longitudinal axis of said blade and embedded in and bonded tosaid body with their spherical centers coinciding with the longitudinalaxis of said blade, said first body of elastomer and plurality of platescooperating to carry substantially solely in compression centrifugalforces imposed on said blade in response to rotation of said rotor hubwhile permitting pivotal movement of said blade about lead-lag andflapping axis and rotation about a pitch axis, said lead-lag andflapping axis intersecting at a generally common point along said pitchaxis, a resilient universal bearing means connected between said bladeand rotor hub and having its axes of greatest stiffness transverse tothe longitudinal axis of said blade and axes of less stiffness about itscenter, said universal bearing means being normally positioned in apredeflected position along the longitudinal axis of said blade duringnon-rotation of said rotor hub and being movable along the longitudinalaxis of said blade to a substantially neutral position in response toresilient movement of said blade relative to said rotor hub as a resultof centrifugal forces imposed on said blade during rotation of saidrotor hub wherein its center is substantially coincident with saidcommon point, so that during normal rotation of said rotor hub,lead-lag, flapping and pitch adjustment and/or movements of said bladerelative to said rOtor hub will be about said common point and forces onsaid blade transverse to the longitudinal axis thereof will be resistedby said universal bearing along its axes of greatest stiffness.
 5. Arotor system, as set forth in claim 4, wherein said resilient universalbearing means comprises an elongate member disposed between said bladeand rotor hub and having its longitudinal axis coincident with thelongitudinal axis of said blade, one end of said member being fixedlyconnected to one of said blade and rotor hub and the other end of saidmember being spherical shaped, the other of said blade and rotor hubhaving means concentrically disposed about said spherical shaped portionof said elongate member, an annular body of elastomer concentricallydisposed about the longitudinal axis of said blade between saidspherical shaped portion of said elongate member and said meansconcentrically disposed about said spherical shaped portion, at leastone annular segmented spherical shaped plate of relatively nonextensiblematerial concentrically disposed about said spherical shaped portion ofsaid elongate member and embedded in and bonded to said annular body ofelastomer for increasing the load carrying ability or stiffness of saidbody along axes transverse to the longitudinal axis of said bladewithout substantially affecting the resistance to movement of said bladerelative to said rotor hub about said lead-lag, flapping and pitch axes.6. A rotor system for a rotary wing aircraft such as a helicopter or thelike comprising a rotor hub rotatable about a central axis, at least onesustaining blade, and means connecting said blade to said rotor hub withsaid blade normally extending generally radially from said hub forrotation therewith about said central axis, said connecting meanscomprising a member fixed to the blade having a first surface extendingtransverse to the longitudinal axis of said blade and spaced from andpresented toward said blade and away from said rotor hub, a member fixedto the rotor hub having a second surface extending transverse to thelongitudinal axis of said blade and spaced radially outward of andpresented toward said first surface, resilient main bearing meansdisposed between said surfaces resiliently restraining said bladeagainst centrifugal forces imposed thereon in response to rotation ofsaid rotor hub while permitting pivotal movement of said blade aboutlead-lag and a flapping axis and rotation about a pitch axis with saidlead-lag and flapping axes intersecting at a substantially common pointalong said pitch axis, a resilient universal bearing means connectedbetween said blade and rotor hub having a center coincident with saidpitch axis, said universal bearing means being normally positioned in apredeflected position along the longitudinal axis of said blade duringnonrotation of said rotor hub and being movable along the longitudinalaxis of said blade toward a neutral position in response to resilientmovement of said blade relative to said rotor hub as a result ofcentrifugal forces imposed on said blade during rotation of said rotorhub to a point where its center is substantially coincident with theintersection of said leadlag and flapping axes with said pitch axis sothat during normal rotation of said rotor hub lead-lag, flapping andpitch adjustments and/or movements of said blade relative to said rotorhub will be about a common point.
 7. A rotor system, as set forth inclaim 6, wherein said resilient universal bearing means comprises asocket carried by one of said blade and rotor hub, a ball spacedinwardly of said socket and carried by the other of said blade and rotorhub, and elastomeric means resiliently interconnecting said ball andsocket.
 8. A rotor system for a rotary wing aircraft such as ahelicopter or the like comprising a rotor hub rotatable about a centralaxis, at least one sustaining blade, and means connecting said blade tosaid rotor hub with said blade normally extending generally radiallyfrom said hub for rotation therewith about said central axis, saidconnecting means comprising a member fixed to the blade having a firstsurface extending transverse to the longitudinal axis of said blade andspaced from and presented toward said blade and away from said rotorhub, a member fixed to the rotor hub having a second surface extendingtransverse to the longitudinal axis of said blade and spaced radiallyoutward of and presented toward said first surface, a first body ofelastomer disposed between and fixedly secured to said surfaces, aplurality of spaced generally concentric segmented spherical shapedplates of relatively nonextensible material disposed transversely of thelongitudinal axis of said blade and embedded in and bonded to said bodyof elastomer with their spherical centers coinciding at a generallyfixed center coincident with the longitudinal axis of said blade, saidfirst body of elastomer and spherical plates cooperating to resilientlyrestrain said blade against centrifugal forces imposed thereon inresponse to rotation of said rotor hub along the longitudinal axis ofsaid blade while permitting pivotal movement of said blade aboutlead-lag and flapping axes and rotation about a pitch axis, which axesintersect at said generally fixed center, a socket carried by one ofsaid blade and rotor hub, a ball spaced inwardly of said socket andcarried by the other of said blade and rotor hub with its center locatedalong said pitch axis and elastomeric means resiliently interconnectingsaid ball and socket, said ball and socket being normally resilientlydisplaced relative to each other axially of the longitudinal axis ofsaid blade during nonrotation of said rotor hub and being movable alongthe longitudinal axis of said blade to a substantially neutral positionwhere the center of said ball is generally coincident with said fixedcenter in response to centrifugal forces imposed on said blade wherebysaid bearings cooperate to resist movement of said blade transverse tothe longitudinal axis of said blade while permitting pivotal androtational movement of said blade about said coincident centers.
 9. Arotor system, as set forth in claim 8 wherein said elastomeric meanscomprises a second body of elastomer and at least one annular sphericalshaped plate of relatively nonextensible material concentricallydisposed between said ball and socket and embedded in and bonded to saidsecond body of elastomer, said plate having its spherical centergenerally coincident with said coincident centers when said ball andsocket are in said neutral position for increasing the load carryingability or stiffness of said second body of elastomer along axestransverse to the longitudinal axis of said blade without substantiallyaffecting the resistance to movement of said blade relative to saidrotor hub about said lead-lag, flapping and pitch axes.
 10. A rotorsystem for a rotary wing aircraft such as a helicopter or the likecomprising a rotor hub rotatable about a central axis, first yoke meanscarried by said rotor hub and extending radially outward therefrom,second yoke means disposed radially outward of said first yoke means, asustaining blade connected to said second yoke means and extendingradially outward from said rotor hub, said yoke means being linkedthrough each other and lying respectively in intersecting planes, saidfirst yoke means having a first surface extending transverse to thelongitudinal axis of said blade facing radially inward toward said rotorhub, said second yoke means having a surface extending transverse to thelongitudinal axis of said blade spaced radially inward of said firstsurface and presented toward said first surface in opposed relationthereto, a body of elastomer disposed between and fixedly secured tosaid first and second surfaces, a plurality of spaced segmentedsphericaL shaped plates of relatively nonextensible materialconcentrically disposed transversely of the longitudinal axis of saidblade and embedded in and bonded to said body of elastomer with theirspherical centers coinciding with the longitudinal axis of said bladeradially from said rotor hub outwardly of said first and secondsurfaces, said body of elastomer and plurality of plates cooperating toresiliently restrain said blade against centrifugal forces imposedthereon in response to rotation of said rotor hub while permittingpivotal movement of said blade about lead-lag and flapping axes androtation about a pitch axis, said axes intersecting at a generally fixedcenter along said pitch axis, and a resilient universal bearingconnected between said first and second yoke means radially outward ofsaid body of elastomer having a center located along said pitch axisresiliently restraining movement of said blade transverse to said pitchaxis while permitting pivotal movement of said blade about said lead-lagand flapping axes and rotation about said pitch axis, the center of saiduniversal bearing being positioned in predeflected position along saidpitch axis from said fixed center during nonrotation of said rotor huband being movable along said pitch axis to a substantially neutralposition where its center is generally coincident with said fixed centerin response to centrifugal forces imposed on said blade.
 11. A rotorsystem as set forth in claim 10, wherein the center of said resilientuniversal bearing is positioned in a predeflected position spaced alongsaid pitch axis from said fixed center radially inward toward said rotorhub.